Analysis and Evaluation Model for Print Mottle using Wavelet Image Denoising Method

Abstract

Print mottle is problematic in the print and paper industry. In this report, a mathematical evaluation model of print mottle was generated after analyzing several methods. The print mottle images can be evaluated by the model based on the theory of wavelet image denoising analyses that use the wavelet multi-scale fast algorithm. The model was then applied to analyze print mottle on four business papers (inkjet papers, newsprint papers, art papers, and double-coated offset printing papers). The correlation between the results of this method and the human visual evaluation system (HVS) was calculated and evaluated. Experimental results showed that the model predictions agreed with HVS results. The correlation between the printed newsprint papers and the eight different wavelet base functions was over 0.76 (such as haar, sym4, bior3.7, etc.) and decomposed at the first, second, and third levels. The results of the three other papers were better matched with the analysis by human eyes, but the correlation of the art paper and visual model were not as strong as the others. The optimal parameters for the print mottle model were presented in the four kinds of papers presented.

Effects on print quality of varying acrylic binder types in water‐based flexographic ink formulations

“…For inks, the binder is a predominant component affecting ink viscosity. 28 Therefore, viscosity and hence ink levelling and setting rate may affect print gloss. To study this among the different binder type formulations, the change of delta gloss between printed ink samples was measured and results are shown in Figure 3.…”

“…In printing, the term “delta gloss” describes the difference in gloss between the printed and the unprinted substrate. For inks, the binder is a predominant component affecting ink viscosity 28 . Therefore, viscosity and hence ink levelling and setting rate may affect print gloss.…”

Back-trap mottle: A review of mechanisms and possible solutions

“…It occurs mostly in solid print areas because uneven printing density or gloss can be easily seen on an image with a large area of homogenous tone. The definition of print mottle in the ISO 13660 (2001) standard states that a periodic fluctuation of the print density at a frequency of 0.4 cycles/mm or less in all directions is print mottle (Fahlcrantz and Johansson 2004;Xu et al 2016), with low-contrast and low-frequency (0.1 to 10 mm) printing unevenness. Näätsaari (2006) showed that the mottling in the frequency range of 2 to 7 mm is the most disturbing to the human eye.…”

Introducing new methods based on the standard ISO/IEC 24790 to evaluate graininess for coloured printed images

“…Having a high correlation with the HVS, wavelet analysis has been widely used in printing quality assessment, especially in evaluating mottling and graininess, two common defects in printed images. 15,16 Wavelets can provide both frequency and spatial information of an image. 17 Since a two-dimensional (2D) image is being evaluated in printing quality assessment, a 2D wavelet transform is used.…”

“…The details are removed in each decomposition level, and the new wavelet transform is applied to the approximation image. 15,18 Due to the enormous developments in machine vision and image processing methods, competitive markets of the printing industry, and abundant efforts to enhance the quality of images, a proper cognition of print defects and their assessment is essential. Therefore, the International Organisation for Standardisation (ISO) has suggested several standards and procedures to evaluate the printing quality, including the standards ISO/IEC 13660 and ISO/IEC 24790.…”